Plume control

Wet/Dry Cooling Tower An Effective Plume Control Method... 

Under certain conditions, the exhaust air of conventional mechanical draft cooling towers may form a fog plume, causing visibility and icing problems to highways and equipment. In cases where this cannot be tolerated, a combination wet/dry cooling tower is shown to be effective fog plume control method. The paper describes the basic phenomena of cooling tower fog formation. The operation and performance characteristics of the wet/dry tower are discussed as well as a method of select wet/dry design criteria. 11 refs, cited. 

Key words groundwater remediation design, optimal plume control, groundwater quality management... 

In the first stage of the solution process, the advective control model seeks a pumping scheme in which the capture zone fully encompasses all control points representing the contaminant plume. The capture zone is simulated by tracking particles from extraction wells backwards through the velocity field. To represent the plume capture constraints numerically, a distance measure is used in which the minimum distance between each plume control point and all particles (see Figure 1) is constrained. When the distance between a control point and particle pathline equals zero then the plume control point lies within the capture zone. To ensure capture of the entire plume, the constraint function must equal zero for all control points. The reverse tracking formulation is stated as... 

Figure I. In reverse tracking, pathlines represent the capture zone and the constraint function measures the minimum distance between a plume control point and all pathlines. Pathlines are shown as dashed curves and the gray area represents the contaminant plume to be contained.

Pumping rates at the two wells shown are systematically altered and the constraint function pk for 108 plume control points is determined. The sum of squared constraint values for each set of pumping rates is shown graphically in Figures 4a and 4b for confined and unconfmed assumptions, respectively. The minimum saturated thickness at the grid cells containing the two extraction wells is also shown on Figure 4b. The optimal solution... 

Figure 5 Three-dimensional plume control problem shown in (a) plan view and (b) projection of plume at y = 1100 m. Dimensions on the left side of (b) indicate the vertical elevations of each layer.

Figure 6. The plume control model must determine the pumping rates from the six candidate wells so that the two plumes are captured. A total of 110 particles are used to represent the plume, a few of which are shown. The horizontal scales are in meters.

The particle tracking-based advective control model described in this chapter is capable of solving two- and three-dimensional plume capture problems with multiple candidate wells and multiple particles in confined and unconfined aquifers. The formulation provides a direct approach to solving plume control problems and uses both forward and reverse particle tracking to exploit numerical characteristics of the two reference frames. 

Shafer, J. M., and Vail, L. W. (1987). Screening method for contaminant plume control. Journal of Water Resources Planning and Management, 113(3), 336-352. 

The plume control concept is used in connection with organic pollutants such as fuels and fuel additives and chlorinated solvents. 

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